1. Field of the Invention
The present invention is related generally to image inspection apparatus, image inspection method, and computer program product.
2. Description of the Related Art
Various apparatuses that inspect whether an image has been printed at a desired position in a desired density have been proposed. For instance, Japanese Patent No. 3523994 discloses an inspection apparatus for inspecting printed patterns formed by repeatedly printing a same single pattern. The inspection apparatus assumes an area where image density varies due to wobbling and/or undulation of a printed medium as a dead zone so as not to take the difference between a reference image and an inspection subject image (hereinafter, “inspection image”) in the dead zone into account. Hence, the inspection apparatus does not detect a deficiency in the dead zone but detects only a deficiency out of the dead zone. An apparatus that monitors fluctuation in color tones on a printout by evaluating integration of a predetermined area of a reference image and that of a comparative image is disclosed in Japanese Patent Application Laid-open No. 2003-266646.
The inspection apparatus disclosed in Japanese Patent No. 3523994 adopts a technique of excluding an area at and near an edge of an image to be inspected so as to take misalignment between the reference image and the inspection image (scanned image) into consideration; however, this technique is disadvantageous in not being capable of accurately inspecting an image (e.g., a line image) that includes only an edge such as a thin line (boundary). Particularly, inspection according to the technique disclosed in Japanese Patent No. 3523994 is not appropriate for a type of misalignment between the reference image and the inspection image that has occurred while a printed medium (paper) is scanned by a scanner. The technique disclosed in Japanese Patent Application Laid-open No. 2003-266646 has no problem when performing comprehensive density inspection because comparison is performed based on integrals of the predetermined area; however, the technique is disadvantageously inappropriate for performing local inspection.